s1 = 'helloworldhelloworld'
new_s = ''
for i in s1:
    if i not in new_s:
        new_s += i
print(new_s)
new_s2 = ''
for i in range(len(s1)):
    if s1[i] not in new_s2:
        new_s2 += s1[i]
print(new_s2)
a = set(s1)
b = list(a)
b.sort(key=s1.index)
print(b)
print(''.join(b))
